The piece, from The Atlantic, seems to criticize researchers for identifying differences without knowing for sure what the differences mean.

The study in question compared magnetic resonance imaging (MRI) scans of 20 “young adult recreational marijuana users” (defined as individuals 18 to 25 who smoke at least once a week but who are not “dependent”), to 20 “non-using controls” (age-matched individuals who have smoked marijuana less than five times in their lives). The researchers reported differences in density, volume, and shape between the nucleus accumbens and amygdala regions of the two groups’ brains—areas hypothesized to affect a wide range of emotions from happiness to fear, which could influence basic decision-making.

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Different-looking brains tell us literally nothing about who these people are, what their lives are like, why they do or do not use marijuana, or what effects marijuana has had on them. Neither can we use such brain scans to predict who these people will become, or what their lives will be like in the future.